Is Sully County, SD in a flood zone?
FEMA's National Risk Index puts Sully County's flood hazard at the 14.1th percentile nationally — among the lowest flood hazard in the country — driven by inland rivers and flash flooding rather than the coast — FEMA's model puts a flood event here at about once every 2 years. County-wide, not parcel-specific: FEMA's real flood-zone map is queried live, never shipped as a download.
Sully County's flood-insurance compliance gap
Sully County is one of the counties where FEMA's own denominator for mandated flood-zone structures is missing, so no compliance rate is shown rather than a guessed one — the data quality guide covers how common this is. Across all residential structures in Sully County, not just the ones FEMA mandates, 0% carry an NFIP policy — most flood damage nationally happens outside the mapped high-risk zone, so that broader number matters too.
Where Sully County ranks
Sully County sits at rank 2733 of 3144 counties on FEMA's flood hazard scale (1 is worst) and rank 3082 of 3144 by population (1 is biggest). Sully County, South Dakota is home to about 1,468 people across 1,006.727 square miles of land.
Checking a specific address in Sully County
Across all of Sully County's 785 residential structures, 0 carry an NFIP policy today — a county-wide count that still can't tell you one address's own mapped zone.
More on how this number was built
The methodology guide shows exactly which FEMA and Census tables feed Sully County's numbers. See the data quality guide for why Sully County, like hundreds of other counties, doesn't get a clean compliance percentage.